US3925435A - Production of isocyanates - Google Patents

Production of isocyanates Download PDF

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Publication number
US3925435A
US3925435A US376298A US37629873A US3925435A US 3925435 A US3925435 A US 3925435A US 376298 A US376298 A US 376298A US 37629873 A US37629873 A US 37629873A US 3925435 A US3925435 A US 3925435A
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United States
Prior art keywords
furoxan
isocyanate
solvent
solution
product
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US376298A
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English (en)
Inventor
John Crosby
Robert Michael Paton
Robert Allan Campbell Rennie
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Imperial Chemical Industries Ltd
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Imperial Chemical Industries Ltd
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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C263/00—Preparation of derivatives of isocyanic acid
    • C07C263/08—Preparation of derivatives of isocyanic acid from or via heterocyclic compounds, e.g. pyrolysis of furoxans
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D271/00—Heterocyclic compounds containing five-membered rings having two nitrogen atoms and one oxygen atom as the only ring hetero atoms
    • C07D271/12—Heterocyclic compounds containing five-membered rings having two nitrogen atoms and one oxygen atom as the only ring hetero atoms condensed with carbocyclic rings or ring systems

Definitions

  • Concentration (moles mole solvent diisocyanate furoxan time(min) I l I l l PRODUCTION or ISOCYANATES This invention relates to the production of isocyanates and preferably, but not exclusively, to the production of aliphatic polyfunctional isocyanates, that is compounds containing two or more isocyanate groups in the molecule. Such compounds are useful, for example, in the production of plastics, for example, polyurethanes.
  • Suitable furoxan starting materials include those of general formula:
  • R and R which may be the same or different, are separate groups in each of which the atom directly linked to the furoxan ring is an aliphatic carbon atom as herein defined.
  • R and R may be linked one to another as part of an aliphatic second ring system (the first ring system being the furoxan ring). This second ring system may itself be part of a multiple ring system.
  • An aliphatic carbon atom is defined as a carbon atom which is not a member of an aromatic ring system.
  • these furoxans may be made to undergo a thermal decomposition and rearrangement to form an isocyanate or a mixture of isocyanates on heating either alone or, preferably, in solution in an inert solvent.
  • An inert solvent is defined as a solvent which will not, at the temperature of the ring-opening reaction, decompose or react at a significant rate with the furoxan, the product isocyanate, or any reaction intermediates.
  • the product isocyanate may then be recovered by conventional means, for example by removal of the solvent by distillation.
  • the product isocyanate may itself react further on heating, for example by dimerization or trimerization of isocyanate groups, and in a batch process the concentration of product isocyanate may decrease after a certain time.
  • FIG. 1 This is shown in FIG. 1, in which the concentration of the reactant furoxan and product isocyanate in a typical reaction according to the invention are plotted against time.
  • the reactant solution may be heated rapidly to the reaction temperature, held there for the optimum time and then the reaction mixture quenched by rapid cooling, but this is inconvenient on a large scale, and it is particularly preferred that the product isocyanate is removed from the reaction zone substantially as it is formed.
  • the product isocyanate is sufficiently volatile, such removal may conveniently be accomplished by distillation of the product from the reaction zone. This may be convenient for example in the preparation of low molecular weight monoisocyanates, for example methyl isocyanate.
  • distillation of the product isocyanate may not always be practicable, particularly when the product is a diisocyanate, and other means of removing it from the reaction zone must then be employed.
  • a preferred mode of operation consists of a process whereby the reactant furoxan flows through the heated reaction zone in a fluid stream, and the product isocyanate is continually swept out of the reaction zone by the fluid stream.
  • the reactants and the product may be in the form of their vapours, the fluid stream comprising the reactant and product vapours and optionally an inert diluent gas.
  • the gaseous fluid stream may be at a pressure lower than 1 atmosphere to facilitate volatilisation of reactant and product.
  • the fluid stream comprises a solution of reactant and product in an inert solvent as hereinbefore defined.
  • the stream enters the reaction zone as a solution of the furoxan reactant, and the temperature and residence time of the stream in the reaction zone are selected so as to optimise the yield and/or conversion of the process.
  • the stream leaves the reaction zone as a solution substantially of the product isocyanate, which may be quenched by rapid cooling to prevent further reaction of the isocyanate.
  • An alternative, less preferred, method of operation comprises including in the system a compound, hereinafter referred to as a trapping agent, which will react rapidly with the product isocyanate to form what may be referred to as a secondary product. Once the decomposition of the furoxan has been completed, the isocyanate may then be regenerated from the secondary product. Optionally the secondary product is isolated and purified before regeneration of the isocyanate.
  • a trapping agent which will react rapidly with the product isocyanate to form what may be referred to as a secondary product.
  • Particularly convenient trapping agents are hydroxylic compounds, particularly high boiling alcohols and phenols. Conveniently, if the boiling point of the hydroxylic compound is high enough, it is used as the solvent for the thermal decomposition of the furoxan. A co-solvent may be employed if desired.
  • trapping agents include amines; substituted phenols, for example p-nitrophenol; and mineral acids, for example, anhydrous hydrogen chloride.
  • the trapping agent is preferably such that the isocyanate can readily be regenerated from the secondary product.
  • the isocyanate may be regenerated by thermal decomposition of the resultant urethane.
  • the temperature at which the isocyanate is produced at a reasonable rate will depend on the structure of the furoxan, but will normally be in the range to 350C.
  • the furoxan is dissolved in a solvent, and the boiling point of the solution is so chosen that the reaction can be carried out at reflux temperature.
  • Suitable inert solvents (or co-solvents) having boiling points in the appropriate temperature range are o-dichlorobenzene (boiling point 179C), l,2,4-trichlorobenzene (boiling point 2l3.5C), l,2,4,5-tetrachlorobenzene (boiling point 244C) and hexadecane (boiling point 287C).
  • the solvent may include or consist of a compound which will react rapidly with the isocyanate and remove it from the reaction zone.
  • Suitable hydroxylic compounds include n-octanol (l-octanol) (boiling point 194C), n-decanol (l-decanol) (boiling point 229C), p-cresol (boiling point 202C), and p-tert-butylphenol (boiling point 237C).
  • the stream may enter and leave a heated vessel constituting the reaction zone, in which the solvent or co-solvent may be under reflux.
  • the flow may pass through a closed system for example a tube surrounded by a heating medium, in which case the solvent or cosolvent will not be under reflux and selection of a suitable boiling point is less critical.
  • a convenient highboiling solvent is n-hexadecane.
  • the structure of the furoxan will vary according to the structure of the isocyanate which it is desired to produce. If the groups R and R are not linked one to another the product will be a mono-isocyanate. It will be apparent that, if the groups R and R are different, then the product will be a mixture of two isocyanates of formulae While the production of such a mixture is within the scope of our invention, it may be preferable for R and R to be identical, giving rise to a single mono-isocyanate.
  • Suitable groups R and R' include C hydrocarbyl groups, for example straight or branched chain alkyl or cycloalkyl groups.
  • the groups R and R may bear subwhere n is an integer of at least 3, preferably 3 to 30, more preferably 3 to and particularly 4 to 10.
  • Dinitrogen trioxide in the form of a premixed stream of nitric oxide and air, is bubbled through a vigorously stirred solution of the olefin in a saturated hydrocarbon-ether mixed solvent, the temperature being maintained between l0 and +l0C.
  • the solid pseudonitrosite formed is separated by filtration and washed, and then converted to the furoxan, either directly, or in two stages via a nitrooxime intermediate.
  • Direct conversion to the furoxan is achieved by heating the pseudonitrosite in the presence of a dehydrating agent such as sulphuric acid or polyphosphoric acid at l00 to 120C. After dilution with water, the product can be extracted with ether and purified by recrystallisation.
  • a dehydrating agent such as sulphuric acid or polyphosphoric acid
  • the pseudonitrosite can be converted in high yield to the Z-nitroalkanone oxime by heating to to l20C in a suitable polar solvent such as dioxane or dimethylformamide until the blue/green coloration of the nitronitroso monomer disappears: removal of the solvent leaves the nitrooxime which can then be converted to the furoxan by heating in the presence of a dehydrating agent such as sulphuric acid.
  • a suitable polar solvent such as dioxane or dimethylformamide
  • the furoxan need not be isolated, but may be converted directly to the isocyanate.
  • n cn CH-CH No, N
  • the methylene groups in the above structures may be unsubstituted, as shown, or may include substituent atoms or groups in place of the hydrogen atoms, provided that such substituents do not react with the dinitrogen trioxide or interfere, sterically or otherwise, with the subsequent reactions. Substituents will carry through to the product isocyanate and will be chosen according to the desired structure of the isocyanate. Certain substituents, for example, sterically hindered groups inducing strain in the alicyclic ring, may aid the production of the isocyanate.
  • the isocyanate is preferably removed from the reaction zone substantially as it is formed. for example, by carrying out the thermal decomposition of the furoxan in a fluid stream comprising a solution of the furoxan in an inert solvent.
  • the alicyclic ring system fused to the furoxan ring may itself be part of an additional ring system.
  • This additional ring system may contain aromatic rings, provided that the ring system directly fused to the furoxan ring is aliphatic.
  • These furoxans may be considered as formally derived from a polycyclic olefin by addition of dinitrogen trioxide across the olefinic double bond.
  • Suitable formal starting materials thus include: norbornene 1f the isocyanate is removed from the reaction zone by reaction with a trapping agent, the secondary product thus produced may itself be a useful material, in which case regeneration of the isocyanate from the secondary product may be omitted.
  • the pump rate was adjusted so as to provide a reaction time of IO minutes for the furoxan solution in contact with the heating bath. Under these conditions the yield of diisocyanate was 46 at 72% conversion.
  • a process for the preparation of aliphatic diisocyanates according to claim 2 comprising the steps of a. bubbling dinitrogen trioxide, in the form of a mixture of nitric oxide and air, through a vigorously stirred solution of a cyclic olefin in a saturated hydrocarbon/ether mixed solvent to form a pseudonitrosite,

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
  • Heterocyclic Carbon Compounds Containing A Hetero Ring Having Oxygen Or Sulfur (AREA)
US376298A 1972-07-21 1973-07-05 Production of isocyanates Expired - Lifetime US3925435A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB3420372A GB1435894A (en) 1972-07-21 1972-07-21 Production of isocyanates

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US3925435A true US3925435A (en) 1975-12-09

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US (1) US3925435A (de)
JP (1) JPS4985024A (de)
BE (1) BE802351A (de)
DE (1) DE2336403A1 (de)
FR (1) FR2193815B1 (de)
GB (1) GB1435894A (de)
IT (1) IT994992B (de)
NL (1) NL7310049A (de)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4029686A (en) * 1974-12-11 1977-06-14 Imperial Chemical Industries Limited Production of isocyanates
US4145360A (en) * 1976-04-01 1979-03-20 Imperial Chemical Industries Limited Production of isocyanates
US4341898A (en) * 1981-05-18 1982-07-27 Air Products And Chemicals, Inc. Synthesis of isocyanates from nitroalkanes
US20080194746A1 (en) * 2007-02-08 2008-08-14 Ping Jiang Rubber composition, process of preparing same and articles made therefrom
US20090111923A1 (en) * 2007-10-31 2009-04-30 Ping Jiang Halo-functional silane, process for its preparation, rubber composition containing same and articles manufactured therefrom

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3275618A (en) * 1962-06-07 1966-09-27 Upjohn Co Processes for preparing alkylene diisocyanates and intermediates therefor
US3275669A (en) * 1962-09-10 1966-09-27 Upjohn Co Preparation of organic isocyanates from n, n'-disubstituted allophanyl chlorides

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3275618A (en) * 1962-06-07 1966-09-27 Upjohn Co Processes for preparing alkylene diisocyanates and intermediates therefor
US3275669A (en) * 1962-09-10 1966-09-27 Upjohn Co Preparation of organic isocyanates from n, n'-disubstituted allophanyl chlorides

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4029686A (en) * 1974-12-11 1977-06-14 Imperial Chemical Industries Limited Production of isocyanates
US4145360A (en) * 1976-04-01 1979-03-20 Imperial Chemical Industries Limited Production of isocyanates
US4341898A (en) * 1981-05-18 1982-07-27 Air Products And Chemicals, Inc. Synthesis of isocyanates from nitroalkanes
US20080194746A1 (en) * 2007-02-08 2008-08-14 Ping Jiang Rubber composition, process of preparing same and articles made therefrom
US7625965B2 (en) 2007-02-08 2009-12-01 Momentive Performance Materials Inc. Rubber composition, process of preparing same and articles made therefrom
US20090111923A1 (en) * 2007-10-31 2009-04-30 Ping Jiang Halo-functional silane, process for its preparation, rubber composition containing same and articles manufactured therefrom
US7816435B2 (en) 2007-10-31 2010-10-19 Momentive Performance Materials Inc. Halo-functional silane, process for its preparation, rubber composition containing same and articles manufactured therefrom
US20110003922A1 (en) * 2007-10-31 2011-01-06 Momentive Performance Materials Inc. Halo-Functional Silane, Process For Its Preparation, Rubber Composition Containing Same and Articles Manufactured Therefrom
US8372906B2 (en) 2007-10-31 2013-02-12 Momentive Performance Materials Inc. Halo-functional silane, process for its preparation, rubber composition containing same and articles manufactured therefrom

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Publication number Publication date
DE2336403A1 (de) 1974-03-21
BE802351A (fr) 1974-01-14
FR2193815A1 (de) 1974-02-22
IT994992B (it) 1975-10-20
FR2193815B1 (de) 1977-02-18
GB1435894A (en) 1976-05-19
JPS4985024A (de) 1974-08-15
NL7310049A (de) 1974-01-23

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